Which conditions of mine air can be determined by measuring devices?

Measuring devices used in mining environments predominantly focus on conditions that directly affect safety and operational efficiency. Temperature, pressure, velocity, and humidity are critical parameters that can be accurately measured and monitored in the mine atmosphere.

Temperature is important for understanding the thermal conditions miners are exposed to and for maintaining equipment. Pressure measurements are vital for assessing air quality and ensuring systems operate within safe limits. Velocity refers to the speed of air movement, which is essential for ventilation purposes, as proper airflow can help dilute harmful gases and maintain breathable air quality. Humidity is also key as it helps to evaluate the moisture level in the mine air, which can affect both working conditions and equipment functioning.

While the other options include some relevant aspects, they do not encompass the precise atmospheric conditions that are typically measured in mining. For instance, altitude is not a direct measurement in underground environments, and factors like longevity and sound do not provide concrete measurements of the mine air's condition. Density, while related to pressure and temperature, is not commonly independently measured in practice as the other four parameters are.